Heather Mills McCartney, estranged wife of Beatles star Sir Paul, is to take legal action over newspaper claims that she worked as a prostitute in her 20s.

Lawyers for the 38-year-old ex-model said the News of the World's claims were "untrue and highly defamatory".

The statement added that legal proceedings would be launched against the paper after her divorce from Sir Paul, 63, was finalised.

The couple announced their separation last month after four years' marriage.

Her lawyers' statement said: "Heather is very distressed by this article.

"She continues to recover slowly from her revision amputation operation and has suffered weight loss, anxiety and sleeping problems as a result of the stress and anxiety of the break-up of her marriage.

"The coverage of this in certain newspapers has caused further distress and illness to her."

The newspaper stories were also called "vicious slurs".

The former model's leg was amputated below the knee after a collision with a police motorcycle as she crossed a road in 1993.

In April she underwent a revision amputation involving the re-attachment of muscle tissue to the bone.

'Intrusion'

She and Sir Paul married in 2002 and have one daughter, Beatrice.

A statement issued last month about their separation said they had "found it increasingly difficult to maintain a normal relationship with constant intrusion into our private lives".

Lawyers for the couple are currently negotiating the terms of their divorce settlement.

Last week Sir Paul said no decisions had yet been made about custody of Beatrice, adding "we have both agreed to work at all times in Beatrice's best interests".